The proposed experiments are designed to achieve a better understanding of patterns of gene expression within the rat brain, to identify and solve the structures of novel brain proteins with restricted expression in the brain, to gain insight into the functions of those proteins in brain physiology, and to harness the cis-acting elements that regulate their transcription for physiological studies. To accomplish these varied goals, we will use an improved method of subtractive hybridization to identify cDNA clones of mRNAs highly enriched in their expression in the rat brain over hypothalamus and push the method so as to isolate clones of all such mRNAs. We will perform pilot experiments using a single-primer PCR-based strategy to survey the expression of about 1000 brain mRNAs in different anatomical sites, developmental stages and physiological paradigms. We will characterize the mRNAs corresponding to clones of regionally enriched mRNAs by determining their complete nucleotide sequences, their sites of expression, the relationship of their encoded proteins with known proteins, the subcellular localization of the protein and the location of the homologous mouse gene on the genetic map. We will use the acquired information to form hypotheses about function and test these by biochemical measurements on the protein expressed in bacteria or Cos cells and by gene inactivation studies. We will characterize 3 newly discovered novel serotonin receptors by mapping their sites of expression within the CNS, isolating their human homologues and determining their pharmacological properties. We will map the sites of expression and biochemical properties of a novel kainate-inducible putative ectopeptidase and test the hypothesis that it is involved in glutamate- dependent associative plasticity. We will assess a model system for targeted gene inactivation and determine the consequence of altering the activities of MAG in neurons or glia and BC1 RNA in neurons. We will test the promoters for anatomically restricted genes in transgenic mice and the effect of cAMP in oligodendrocyte inactivation.